In recent years,the application of a lining material onto the surface of the above described pipe lines buried in the ground is carried out for the purpose of repair and reinforcement of the pipe lines when superannuated. One of the lining method is carried out in such manner that a lining material in the form of a tube is provided on the inner surface thereof with a binder and the lining material is inserted into a pipe line and allowed to advance therein while turning the lining material inside out under fluid pressure whereby the lining material is bonded onto the inner surface of the pipe line with the binder being interposed between the lining material and the pipe line (see, for example, U.S. Pat. Nos. 4,368,091 and 4,334,943 and Japanese Patent Publn. Nos. Sho. 58-38088, 58-51654 and 59-12911). This method need not dig up a pipe line over its full length and is operable simply by forming manholes at both terminal ends of the pipe line to be lined. The lining work itself can be done within a short period of time for a long pipe line and is operable for a pipe line having a number of bends, thus being regarded as an excellent method.
On the other hand, various kinds of lining materials have been proposed as the lining material for the lining method of this type, including a thin flexible plastic tube, a textile lining material which comprises a woven or non-woven fabric in the form of a tube provided on the exterior surface with an air-or water-impervious coating, etc.
In Japanese Patent Publn. No. Sho. 55-43890 (British Patent No. 1,449,455), for example, there is disclosed a lining material which is composed of a flexible resin-absorbing material comprising felt and/or fabric and a flexible foamed agent and having an impervious film coated thereon. Japanese Patent Publn. No. Sho. 58-33098 discloses a lining material manufactured from a flat web laminate comprised of resin-absorbing layers with an impervious layer on one side thereof, the both ends of which have been sewn with a thread to form a tubular shape having the impervious layer on the external surface, the sewn area being fully covered with a sealing ribbon or a coating as well as a method for manufacturing the lining material. U.S. Pat. Nos. 4,334,943 and 4,368,091 disclose a lining material comprising a textile jacket made of warps and a weft woven in a tubular form and overlaid with a resin. Further, Japanese Laid-open Utility Model Appln. No. Sho. 56-3619 discloses a lining material comprised of a similar tubular textile jacket having a flexible rubbery or plastic coat on the exterior surface thereof. In Japanese Laid-open Patent Appln. No. Sho. 56-8229 aiming at an improvement of the above lining material for pipe lines, there is disclosed a lining material comprised of a tubular textile jacket made of fibers woven into a tubular form having a coat of a flexible rubbery or plastic material on the external surface thereof and capable of expanding by 7-15% in outer diameter when a pressure equal to the minimum fluid pressure is applied. In Japanese Patent Appln. No. Sho. 58-102361, there is disclosed a lining material for pipe lines which is comprised of a tubular textile jacket consisting of warps and a weft made of synthetic fibers and woven in a tubular form laminated on its outer or inner surface with another tubular textile jacket having a given thickness and interstices in its interior and having on the exterior surface thereof an air-impervious layer of a synthetic resin.
On the other hand, when the pipe-lining methods of the above mentioned type are applied to pipe lines for transporting fluids, such as gas conduits, city water pipe lines, sewage pipes, oil pipe lines, etc., a tubular lining material used for these methods was originally required to possess a property of not permitting any leakage of the fluid being transported, flexibility capable of adapting the lining material in compliance with pipe lines even in curved portions, strength capable of withstanding the internal pressure of the fluid, durability of the coat, etc. As the pipe-lining methods of this type have been spread widely, however, various characteristics have been required for the tubular lining material according to the environment of the pipe lines to be treated and the nature of ground. At present, the following properties are required for the lining material:
(1) Earthquake-resistance:
In case a pipe line for transporting a fluid is cracked or broken by a strong external force such as earthquake, the lining material should be peeled off from the pipe line, without being destroyed together with the pipe line, to maintain by itself the function of a passageway for transporting the fluid. For this purpose, the lining material should have a combination of the earthquake-proofing propert and the earthquake-absorbing property. Such specific characteristics are defined hereinafter as "earthquake-resistance." In order to furnish a lining material with the earthquake-resistance, the lining material should possess a sufficiently high tenacity in lengthwise direction and a strength to such a degree that the lining material should not be broken down prior to shearing destroy of a binder. In case the pipe line buried in a soft ground or reclaimed land is cracked, broken off or disconnected by dip of the ground or the like cause, the lining material possessing the earthquake-resistance can maintain the function of a passageway to avoid any trouble. In recent years, possibility of earthquakes is predicted in many places according to the development of earthquake-predicting techniques. Thus, the earthquake-resistance is an important characteristic property for lining materials for pipe lines in districts where occurrence of earthquake is anticipated.
(2) Shape-maintaining property against external hydraulic pressure:
In case the pipe line is corroded to form a hole, the lining material should not be collapsed by the hydraulic pressure of underground water entered through the hole to narrow the flow path inside the pipe line. When the pipe line is broken off by earthquake or the like, the external pressure will directly be applied to the lining material. Thus, the lining material should also withstand this pressure. The performance capable of withstanding the external pressure without being collapsed to maintain the flow path is important for the lining material and is defined herein as the shape-maintaining property against external hydraulic pressure. The water-resistance and hardness of the binder are important for furnishing the lining material for pipe lines with the shape-maintaining property against external hydraulic pressure. It is further necessary that the binder has a sufficient thickness. Thus, the lining material is required to be impregnated with a sufficient amount of a binder.
From the past, epoxy resins, unsaturated polyester resins, acrylic resins and urethane resins are used as a binder of this type. As a pipe line may be constructed under the ground where underground water is intruded, the binder is required to have such property that the curing reaction proceeds without being disturbed even in water to effect cohesion and that the cohesive strength is not reduced by the influence of water after curing. From this viewpoint, unsaturated polyester resins and acrylic resins using a peroxide as the curing agent are not preferable as they may not be cured in the coexistence of water. Further, they are not desirable in the aspect of using styrene monomer as a solvent. Urethane resins are curable in water but troublesome in adjustment of their pot life, etc. and is not preferable in that the monomeric components are sometimes soluble in water, thus causing environmental pollution. Thus, binders suitable for the lining materials used for a pipe line of this type are epoxy resins among which those using an aromatic or aliphatic polyamine as a curing agent are preferred because they can be cured with certainty even in water.
However, it is difficult to reduce the viscosity of such epoxy resins, so that some device becomes necessary for impregnating the fibrous layer reliably with the resins. Even in case a thick fibrous layer has been impregnated with the epoxy resins, it is difficult to make the whole layer completely water-impervious so that a percolating phenomenon with water occurs under external hydraulic pressure. Consequently, the resinous film is also influenced by the external hydraulic pressure so that the film may, if its adhesion strength to the fibrous layer is weakened, be peeled off from the fibrous layer to block the flow path of a fluid. Thus, a higher adhesion strength between the resinous film and the fibrous layer is required as one of the conditions for withstanding the external hydraulic pressure. Since the shape-maintaining property against external hydraulic pressure depends on the thickness of the lining material, the fibrous layer used in the form of multiple layers has to be integrated entirely with a binder.
(3) Internal pressure-resistance:
In case a fluid-transporting pipe line is broken off, its lining material will withstand the fluid pressure. Thus, the lining material is required to be tolerant to the fluid pressure. Further, the lining material should not be broken, when it is applied to the pipe line, by fluid pressure necessary for evagination of the lining material. The lining material is thus required to have a considerable pressure-resistance.
(4) Flexibility:
In case of applying a lining material to a pipe line, the lining material is evaginated under fluid pressure. Thus, the lining material is required to be flexible and does not need any high pressure for evagination. This property is important since evagination of the lining material having a thick fibrous layer is difficult.
The above described prior art lining materials can satisfy a part of these necessary properties but fail to satisfy all of these properties.
For example, the lining materials disclosed in Japanese Patent Publn. Nos. Sho. 55-43890 and 58-33098 basically employ an unwoven fabric and can afford a lining material having a sufficient thickness as adjustment of the thickness is possible. However, the lining materials lack the earthquake-resistance because of poor strength of the unwoven fabric itself and are devoid of a device for being impregnated with an epoxy resin with certainty. The internal pressure-resistance of the lining materials is poor because of using the unwoven fabric, and moreover, there is found no means for enhancing the adhesion strength between the resinous film and the fibrous layer.
The lining materials disclosed in Japanese Laid-open Utility Model Appln. No. Sho. 56-3619 and Japanese Laid-open Patent Appln. No. Sho. 56-8229 basically employ a woven fabric and are extremely high in strength. The lining materials can further be enhanced in strength by modifying the fabric structure so that they may have increased earthquake-resistance and internal pressure-resistance, but on the other hand are difficult to increase the thickness of the fabric. In case of fabrics for general clothing, it is not difficult to obtain thicker fabrics by making device for the fabric structure. A tubular textile jacket for lining materials is woven in a tubular form by a rotary weaving machine which, however, cannot weave a fabric with a complicate structure. The fabric has to be woven thickly and furnished with a high tenacity as described above, but the thickness cannot be increased merely with a wadding or backing unlike a thick fabric for clothing. Although the use of thick threads may increase the thickness of fabrics, stiffness of the threads makes it difficult to evaginate the lining material on its application to pipe lines. Further, the surface of the fabric becomes coarse so that the flow resistance to a fluid to be transported is increased. The use of too thick threads makes the texture coarse so that the binder cannot be kept only with the fabric itself to deteriorate the shape-maintaining property against external hydraulic pressure. No consideration is made for the improvement in adhesion strength between the fabric layer and the resinous film.
The lining material disclosed in Japanese Patent Appln. No. 58-102361 satisfies all of the above mentioned necessary characteristic properties to a certain degree but there is made neither device on impregnation with a binder, especially on the means for fully impregnating an unwoven or woven fabric as a tubular textile jacket with an epoxy resin nor consideration on increase in adhesion strength between the tubular fabric and the resinous film and between the tubular fabric and the tubular unwoven fabric.
In such situation, there was a great demand for making further improvement in the lining material disclosed in Japanese Patent Appln. No. Sho. 58-102361 to develop an improved lining material which satisfies all of the above mentioned characteristic properties necessary for lining materials. The present invention has been accomplished, paying attention to the above situation, to make further improvement in the lining material disclosed in Japanese Patent Appln. No. Sho. 58-102361.
It is an object of the present invention to provide a lining material utilizable for pipe lines, especially those buried in the ground, which possesses a combination of the earthquake-resistance and the shape-maintaining property against external hydraulic pressure without deteriorating flexibility, properties for impregnation with a binder and internal pressure-resistance being in the possession of the prior art lining materials.
It is another object of the present invention to provide a lining material for pipe lines, which uses a tubular woven fabric and a tubular unwoven fabric as a tubular textile jacket and is improved in the properties for impregnation with a binder and the adhesion strength between the resinous film and the tubular woven fabric and between the tubular woven fabric and the tubular unwoven fabric and furnished further with the earthquake-resistance and the shape-maintaining property against external hydraulic pressure without deteriorating the characteristic properties own by the prior art lining materials.
It is still another object of the present invention to provide a lining material which uses a tubular woven fabric together with a tubular unwoven fabric of a special shape and structure having been placed inside the tubular woven fabric as a tubular textile jacket and satisfies all of the characteristic properties required for the lining materials for pipe lines.